He made the company this much larger in just one generation.
Koichi went to take a once-in-a-lifetime gamble.
He amassed an enormous fortune over the course of his lifetime and his son doubled it.
This word has the kanji for one and period. You only have one period to live in so this is the only lifetime you get. Unless you're reborn, but that will probably be in the next age, not this one. So one lifetime for you!
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.